Implantable electrode arrays may be used to deliver therapy to patients to treat a variety of symptoms or conditions such as chronic pain, tremor, Parkinson's disease, epilepsy, urinary or fecal incontinence, sexual dysfunction, obesity, or gastroparesis. For example, an implantable medical device may deliver neurostimulation therapy via leads that include electrodes located proximate to the spinal cord, pelvic nerves, peripheral nerves, the stomach or other gastrointestinal organs, or within the brain of a patient. In general, the implantable medical device may deliver electrical stimulation therapy in the form of electrical pulses via one or more electrodes carried by one or more implantable leads. Alternatively, electrical stimulation may be delivered by electrode arrays associated with leadless stimulators.
A clinician selects values for a number of programmable parameters in order to define the stimulation therapy to be delivered to a patient. For example, the clinician may select an amplitude, which may be a current or voltage amplitude, and a pulse width for a stimulation waveform to be delivered to the patient, as well as a rate at which the pulses are to be delivered to the patient. The clinician may also select particular electrodes within an electrode array as an electrode combination to be used to deliver the pulses, and polarities of the selected electrodes. In some cases, for current-based systems, electrodes may be identified as source or sink electrodes. A group of parameter values may be referred to as a program in the sense that they drive the stimulation therapy to be delivered to the patient.
Modern neurostimulation systems typically support a variety of electrode array configurations. Different leads, for example, may vary in number of electrodes, shapes and sizes of the electrodes, and spacing between individual electrodes. A patient may have one or more leads, possibly of varying shapes and sizes, implanted to address a particular disease state. Characterization of the types of leads implanted within a patient and the relative positions of the leads and electrodes may be of interest to the caregiver. However, the complexities of modern electrode arrays and uncertainty with respect to implant location and optimum target tissue can make characterization of implanted electrode arrays difficult.